Interactions between different species are important in living organism and in industrial systems. The immune system is a first example, where antibodies in the bloodstream interact with pathogens and thereby guide natural killer cells to the pathogen. Therapeutic drugs is a second example, where a drug may interact with an enzyme in a way that inhibit the enzyme activity. A third example is detection of diseases in humans or animal, by contacting a sample from the human or animal with a liquid containing a species that interacts specifically with the pathogen causing the disease. If the species remains on the sample after a wash step, the sample is carrying the pathogen causing the disease. Exactly the same method can be used to detect contamination in food stuff. This means that methods and devices for characterization of interactions between species are important not only for research and diagnostics in biology and medicine, but also in quality control and characterization assays in a variety of fields.
There are many known methods for characterizing the interaction between two or more species. One common method is to attach one species to a solid support and add a second bifunctional species dissolved in liquid. The bifunctional species should (a) have a property that is easily detectable (e.g. be radioactive or have a fluorescent moiety attached to it) and (b) interact with the species that is attached to the solid support. The liquid is brought into contact with the solid support, sometimes followed by a wash of the solid support in a liquid without the bifunctional species. If the bifunctional species interacts stably with the species on the solid support it will accumulate on the solid support and remain there after a wash. Presence of the bifunctional species can then be detected. Another, more complicated method that has been widely used for the characterization of interactions is enzyme linked immunosorbent assay (ELISA).
The present invention aims at facilitating the characterization of how species interact with each other. The method is particularly suitable when one of the species is large (in a molecular context), e.g. if one of the species is cells or bacteria.